Components for the hot gas path in gas turbines are made from Ni- or Co based materials. These materials are optimized for strength and are not able to withstand oxidation and/or corrosion attack at higher temperatures. Therefore, these kinds of materials must be protected against oxidation by MCrAlY-coatings which can be used as bondcoats for thermal barrier coating (TBC) systems as well. In TBS systems, the MCrAlY coating is needed against hot gas attack on one side and on the other side this coating is needed to adhere the TBC to the substrate Improving such systems against oxidation will lead to increased bondcoats service temperatures with increased life properties.
To protect the materials against hot corrosion/oxidation, MCrAlY overlay coatings are coated mainly by low pressure plasma spraying (LPPS), air plasma spraying (APS), electron beam physical vapor deposition (EBPVD), cold spray (CS) or high velocity oxy-fuel (HVOF) process. The MCrAlY coating is based on nickel and/or cobalt, chromium, aluminum, silicon, rhenium and rare earth elements like yttrium. With increasing bondcoat temperatures, these coatings can fail which can lead to spallation of the thermal barrier coating. Therefore, with increasing service temperatures, improved coatings are needed to withstand the oxidation attack. Additionally this kind of coatings should have acceptable thermo-mechanical properties. These requests can only be achieved by an optimized composition of the bond coat.